Training a Magikarp has always been a tricky proposition in Pokemon games: With no moves, the giant fish is practically useless in battle. That tradition doesn't just continue in Pokemon GO, it is taken to the next level. Look at Magikarp's evolution requirements in Pokemon GO. Just look at them:
Four hundred candies. Most monsters in Pokemon GO don't have such ridiculous requirements -- the highest candy count I've seen is 100, and that's for the third evolution in a line. It's possible that Magikarp is the hardest monster to evolve in the entirety of Pokemon GO at the moment, which is amazing.
I don't know how long it will take me to evolve my Magikarp; they don't spawn very often near where I live or work. But even if you're in the middle of a Magikarp nest, actually collecting 400 Magikarp candies is still a slow grind. Contrast this to the games, where it's pretty easy to just use an XP share item or whatever. You don't even have to think about training Magikarp, the items do it for you.
More so than the main games, evolving a Magikarp in Pokemon GO is a real accomplishment. I commend any of you who are attempting this hilarious challenge. The Gyarados will be oh-so-worth it.
In the meantime, it's pretty amusing to see people reacting to Magikarp in Pokemon GO:
And if you're looking to get started with Pokemon GO, make sure to check out our How To: